1. Field of the Invention
The present invention relates to a linear ball bearing unit and more particularly, to a linear ball bearing unit of the kind having a track shaft extending therethrough. The unit essentially comprise a bearing body with a pair of symmetrically located ball rows provided thereof, retainer-cover assemblies secured to the end faces of the bearing body and having in integral combination a retainer and a cover, an upper slide member and a pair of symmetrically located side slide members. The upper slide member and side slide members are disposed between the bearing body and the track shaft.
2. Description of the Prior Art
A linear ball bearing is usually constructed in such a manner that side covers at the end faces of the bearing body are formed separately from retainers which are incorporated in the bearing body (as shown in U.S. Pat. No. 4,040,679, U.S. Pat. No. 4,253,709 and U.S. Pat. No. 4,296,974).
The conventional retainers are made of steel plate by press working. They are so designed as to include a plurality of axially extending slits located at a predetermined position and tongues projected from both ends of the slits, these tongues are intended to scoop balls when the latter enter and leave the slit. Due to the structure of the retainers as described the tongues require high mechanical strength and wear resistivity.
To meet these requirements, a strong steel material is employed for the retainers. This steel material is subjected to heat treatment such as quenching, annealing or the like after completion of press working. As a result they are manufactured at a great cost.
When a machining operation is conducted for a workpiece firmly mounted on a carriage, the linear ball bearing onto which the carriage is fixedly secured is moved to a predetermined position and then it is locked. However, the conventional linear ball bearing requires a clamp mechanism for ensuring the locking of the carriage. This clamp mechanism is arranged separately from the bearing unit in such a manner as to effect clamping on the track shaft.
The arrangement of the clamping mechanism on a metal working machine causes the space which is occupied by the entire machine to be enlarged, resulting in increased inconvenience when operating the machine.
Thus, the present invention is intended to obviate the drawbacks inherent to the convention linear ball bearing units.